1 86 Charles Darwin. 



everywhere, at a depth not greater than fifteen hun- 

 dred fathoms, it was composed of these organisms. 

 They filled the water, floating about, and in such 

 numbers that it has been estimated that if they are 

 as numerous, down to a depth of six hundred feet, 

 as they are near the surface, there would be more 

 than sixteen tons of calcareous shells or carbonate 

 of lime in the uppermost one hundred fathoms of 

 every square mile. 



These little creatures are continually dying, and 

 the result is that a constant shower of their shells is 

 dropping upon the bed of the ocean, and slowly 

 tending to fill it up ; how slowly can be understood 

 from the minuteness of the animals. Yet we know 

 that the enormous deposits of chalk, represented by 

 the Dover cliffs, were formed by this silent rain. 



The pyramids of Egypt are deposits of a small 

 shell — nummulite ; their accumulations on some 

 ancient sea-bed forming the stone which was cut 

 and piled up by the ingenuity of man. We wonder 

 at these monuments, but how much more wonderful 

 is the age they represent in the history of nature. 



In England the Paleozoic strata is 57,154 feet in 

 depth; the Secondary strata 13,190 feet; and the 

 Tertiary strata 2,240, according to Professor Ramsey; 

 in all, 72,584, or about thirteen miles of rock which 

 has been piled up by animal deposits inch by inch. 



Those who are careful observers, and who return 

 to localities after an absence of many years, rarely 

 notice any difference in a landscape. America has 

 been inhabited by the white race for six hundred 

 years, yet there has been little or no change in the 



